It is necessary in breath alcohol measuring devices to calibrate these at regular intervals in order to ensure that the displayed measured value corresponds to the actual alcohol level that is contained in the breathing air blown into the device.
It is sufficiently well known for this purpose that the devices in question are recalibrated by a correspondingly trained mechanic in a service facility, while the breath alcohol measuring device is exposed to a test gas that has a known alcohol content. Such a calibration performed by a service facility is extraordinarily expensive and therefore disadvantageous for the user.
Moreover, it is known from U.S. Pat. No. 6,526,802 B1 that a water-ethanol calibrating liquid is evaporated in a closed container, and this vapor is admitted to the breath alcohol measuring device in order to supply this with a gas having a defined alcohol concentration. However, the operation of such a device has also proved to be extraordinarily complicated.